Date: Wed, 25 May 2011 17:50:07 GMT From: Warner Losh <imp@bsdimp.com> To: freebsd-bugs@FreeBSD.org Subject: Re: misc/145395: [nanobsd] [patch] Extremely slow nanobsd disk image creation and 100% disk load on zfs Message-ID: <201105251750.p4PHo7c9027992@freefall.freebsd.org>
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The following reply was made to PR misc/145395; it has been noted by GNATS. From: Warner Losh <imp@bsdimp.com> To: Alex Bakhtin <alex.bakhtin@gmail.com> Cc: bug-followup@FreeBSD.org, imp@FreeBSD.org Subject: Re: misc/145395: [nanobsd] [patch] Extremely slow nanobsd disk image creation and 100% disk load on zfs Date: Wed, 25 May 2011 11:38:46 -0600 If you are doing soft updates, you can't do async. They are mutually = exclusive. Soft updates usually are a big win for creation, but might = need to be turned off for async operations. If you have an updated patch against -current, please let me know. Warner On May 25, 2011, at 7:35 AM, Alex Bakhtin wrote: > Hello, >=20 >=20 >> From-To:open->closed >> By:imp When:Fri May 13 13:44:33 MDT 2011 >> Why:We've been doing async for a while now. Bug OBE. >=20 > I'm really sorry, but today I have tested the nanobsd.sh from > 9-CURRENT and I'm completely sure that the problem WAS NOT fixed. I > discovered that building image is still extremelly slow and produces > great disk load. After checking deeply, I found that image is not > mounted in async mode. >=20 > /dev/md2s1a on /mnt/system/obj/amtkit/_.mnt (ufs, local, soft-updates) >=20 > I tried to mout in async manually - and it seems that async option > is ignored for MD-backed filesystem: >=20 > bakhtin@tarzan(14) /mnt/system/nanobsd/amtkit >> sudo umount /mnt/system/obj/amtkit/_.mnt >=20 > bakhtin@tarzan(14) /mnt/system/nanobsd/amtkit >> sudo mount -o async /dev/md2s1a //mnt/system/obj/amtkit/_.mnt >=20 >> mount | grep md > /dev/md0 on /etc (ufs, local) > /dev/md1 on /var (ufs, local) > /dev/md2s1a on /mnt/system/obj/amtkit/_.mnt (ufs, local, soft-updates) >=20 > As you can see - md2s1a is not mounted in async mode, and this causes > extremely bad performance on ZFS. >=20 > I'm pretty sure that attaching MD in async mode fixes this problem. > Please review my patch and this bug. >=20 >=20 > -- > --- > Alex Bakhtin >=20 >=20
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